Modern telephone systems allow multiple parties at different locations to hold a conference. However, telephone conferences do not provide all of the conveniences of a face-to-face conference, where participants all meet at a common table in a meeting room.
For example, in a meeting room, participants can view an object of interest, such as a drawing or a product. Such viewing is not possible in a telephone conference.
The invention concerns systems for collaborative video conferencing, using the telephone system. The invention generates a common visual image which is distributed to several computers. The users of the computers can make annotations on the common image. When they do, the invention replicates the annotations on all displays of all computers.
Under the invention, the annotation does not corrupt the basic image, or document, which is annotated. Further, the invention concerns a particular type of annotation, namely, highlighting.